Question

What is the sum of the geometric sequence 2, 10, 50, … if there are 7 terms?

Answer 1

Sn = a1 (r^n - 1)
----------
r - 1

S10 = 2 * (5^7 - 1)
---------- = 39062
5 - 1

Answer 2

Answer: The sum of the given G.P is 39062

Explanation:

Since, the sum of a G.P. is,

`S_(n)=(a(r^n-1))/(r-1)`

( If r > 1 )

Where r is the common ratio, a is the first term and n is the number of terms.

Here, the given G.P. is,

2, 10, 50, … up to 7 terms

⇒ a = 2, r = 5 and n = 7,

Thus, the sum of this series,

`S_(7)=(2(5^7-1))/(5-1)`

`=(2(78125-1))/(4)`

`=(156248)/(4)=39062`